The present invention relates to a dry shaver with a height adjustable cutter head, and more particularly to the shaver having a floating cutter head which is capable of being depressed equally at different positions but against differing biasing forces.
A shaver with a floating cutter head is known in the art, for example, in U.S. Pat. No. 5,398,412 to be advantageous for making it easy to move the cutter head in smooth contact with various portions of a user""s face for effective shaving. The cutter head comprises a head frame which carries an outer cutter and is mounted on top of a shaver housing. An inner cutter is urged by a bias spring into pressed contact with the outer cutter and is driven to move relative to the outer cutter for shearing the hairs. The head frame is floatingly supported to the shaver housing so that the cutter head can be depressed while compressing the bias spring. Thus, the biasing force of the spring increases as the cutter head is depressed. When the user intends to shave the hard hairs, the cutter head is depressed deeply to increase the biasing force, i.e., the contact pressure between the outer cutter and the inner cutter for successfully shearing the hard hairs with the increased contact pressure. The deeper the cutter head is depressed to increase the contact pressure, the more the skin experiences a counter-pressure from the outer cutter. The counter-pressure is inevitable for the shaving, but should be kept within a tolerable range since too-much counter-pressure can irritate the skin. However, when shaving the hard hairs with the floatingly supported cutter head of the above patent, the cutter head has to be depressed deeply with an attendant increase in the counter-pressure. In other words, the shaving of the hard hairs is made only after the cutter head is depressed deeply at the sacrifice of the increased counter-pressure, while the shaving of the soft hairs can be made even without depressing the cutter head and therefore only at a slight counter-pressure to the skin. Consequently, in order to reduce the skin irritation, it is highly desirable that the cutter head gives a reduced counter-pressure to the skin even for shaving the hard hairs with the increased contact pressure between the outer and inner cutters.
In the meanwhile, Japanese Patent Early Publication (KOKAI) No. 60-176679 discloses one solution of adjusting the contact pressure between the outer cutter and the inner cutter. The outer cutter is fixedly mounted on top of a shaver housing, while the inner cutter is urged by a bias spring against the outer cutter. The bias spring is supported to a drive element for the inner cutter and is compressed between the inner cutter and the drive element for giving a suitable contact pressure between the outer cutter and the inner cutter. The contact pressure is adjusted by varying a compression amount of the bias spring with the outer cutter being kept in a fixed position. Since the outer cutter is not capable of being depressed in a direction of varying the compression amount of the bias spring, the contact pressure has to be adjusted by use of an actuator which is connected to the bias spring or to the drive element for directly deforming the bias spring or moving the drive element of the inner cutter towards and away from the outer cutter. The actuator moves together with the drive element, i.e., the inner cutter and therefore gives rise to a considerable friction with a handle mounted on the shaver housing for manipulation of the actuator, thereby inevitably developing an additional friction at the interconnection between the moving actuator and the handle, which should be avoided for reducing noise and power consumption.
The present invention has been accomplished in view of the above insufficiency to provide an improved dry shaver which is capable of being depressed equally at different positions but with differing contact pressures between the outer and inner cutters. The shaver in accordance with the present invention comprises a housing having a motor and mounting the outer cutter and the inner cutter at its upper end. The inner cutter is driven by the motor to move in shearing engagement with the outer cutter for shaving the hairs. The inner cutter is urged upwardly by a bias spring to develop a contact pressure at which the inner cutter is pressed against the outer cutter. The outer cutter is carried by a cutter holder which is movably supported to a head frame mounted on top of the housing. Included in the shaver is a height adjust mechanism for adjusting the height of the head frame relative to the housing between a high position and a low position while compressing the bias spring differently to vary the contact pressure, and for allowing the cutter holder to be depressed relative to the head frame at each of the high and low positions. Therefore, in addition to that the outer cutter can be depressed further even at the low position when shaving the hard hairs, the hard hair shaving can be initiated at the low position where the increased contact pressure is available but with the outer cutter being held undepressed relative to the head frame, and therefore without exerting the increased counter-pressure to the skin, thereby enabling to shave the hard hairs successfully with the increased contact pressure but without irritating the skin. Stating differently, the increased contact pressure effective for shaving the hard hairs can be initially set without depressing the outer cutter which would otherwise increase the counter-pressure on the skin. Shaving of soft hairs can be made with the head frame held at the high position where the outer cutter is allowed to follow the contour of the skin only accompanied with less counter-pressure on the skin and where the contact pressure is low but sufficient for shaving the soft hairs.
Accordingly, it is a primary object of the present invention to provide an improved dry shaver which is capable of shaving the hard hairs successfully and easily in a like manner as shaving the soft hairs.
Preferably, the head frame has a head cover projecting on top of the housing to surround the outer cutter in such a way that the outer cutter exposed on the head cover. The height adjust mechanism is interlocked with the head cover so as to move he head cover together with the head frame between the high and low positions. Thus, the outer cutter is kept exposed on the head cover equally irrespective of the high and low position that the head frame takes, assuring convenient shaving of the hairs while varying the contact pressure.
The inner cutter is driven to move by a drive element projecting on top of the housing. It is this drive element that mounts the bias spring with one end of the spring retained to the drive element and with the other end of the spring being held in pressed contact against the inner cutter, developing the contact pressure between the outer and inner cutters. Thus, as the outer cutter, i.e., the head frame is depressed deeper, the contact pressure will increase for facilitating the shaving of the hard hairs.
In a preferred embodiment, the height adjust mechanism comprises a handle and a slider which is actuated by the handle to vertically move the head frame. The slider has an upper end projecting on top of the housing for detachable engagement with the head frame, enabling the head frame to be removed from the housing for cleaning of the shaver.
The housing is formed on its top wall with a fixed mount frame for detachably mounting the head frame. The mount frame has a peripheral wall projecting on top of the housing in an overlapping relation with the head frame along the entire periphery of the housing irrespective of the position of the head frame relative to the housing. With this arrangement, it is readily possible to retain the sheared hairs within the confines of the top periphery of the housing and prevent undesired scattering of the hairs outwardly through the interface between the head frame and the housing.
The housing may be composed of a main case and a front cover. The main case has a water-tightly sealed interior space for accommodating the motor and carries the drive element extending in a water-tight fashion from the motor through a top of the main case for driving connection with the inner cutter. The front cover is placed over the main case to form therebetween a compartment which is separated from the water-tight sealed interior space. The handle is partly disposed in the compartment and is exposed on the exterior of the front cover. The slider is movably supported to the main case exteriorly of the water-tight sealed interior space to have its one end connected to the handle and the other end connected to the head frame. Thus, the height adjusting mechanism composed of the handle and the slider can be isolated from the sealed space and therefore can be added to the shaver while keeping water-tight sealing of the motor and associated electrical parts.
The handle is preferably realized as a dial rotatably mounted on the housing to translate the rotary motion of the dial into the vertical movement of the slider. The slider may be provided with a rack which is in meshing engagement with a gear of the dial.
A latch may be provided to engage with the dial in order to hold the head frame at the high and low positions, as well as an intermediate position.
The housing may be provided with an additional motor for driving the slider to move vertically when adjusting the position of the head frame.
Preferably, the slider is formed at its upper end with a hook for detachable engagement with the head frame and at its lower end with a joint for engagement with the dial. The dial is fixed to the housing with respect to a vertical direction in which the head frame is allowed to move. The slider has a resilient leg connecting the hook and the joint so as to permit the head frame engaged with the hook to resiliently move in the vertical direction relative to the housing. With this arrangement, the resilient leg can absorb an impact possibly applied to the head frame when the shaver is dropped on the floor, thereby protecting the outer cutter as well as the height adjusting mechanism.
In this connection, the shaver is provided with a restrictor which restricts an extent to which the head frame is permitted to resiliently move relative to the housing. The restrictor comprises a rigid guide which is actuated by the dial to move vertically together with the slider and which is formed with a vertically elongated slot for loosely receiving a stud formed on the slider between the hook and the resilient leg. The stud is engaged with the slot such that the stud is only allowed to move vertically within the slot for restricting the resilient movement of the head frame. Preferably, the slider is formed as a single piece to have the resilient leg integrally formed with the hook and the joint.
In the preferred embodiment, the dial is rotatably supported to the housing to rotate about a rotary axis and is formed with a cam groove for engagement with a cam follower projecting on the slider. The cam groove is made eccentric with respect to the rotary axis so as to translate the rotary motion of the dial into the vertical movement of the slider. The cam groove may be an endless annular groove extending about the rotary axis so that the dial can be rotated continuously in either direction for adjusting the height of the head frame. The cam groove is preferred to have a curvature varying along its path from a minimum curvature to a maximum curvature. The cam groove is engaged with the cam follower at a portion having the minimum curvature when the slider moves the head frame just around the low position. In this consequence, the cam follower travels less distance with respect to a radial direction of the dial per unit angular movement thereof, thereby enabling to manipulate the dial softly but sufficiently against the increased force due to the depressed bias spring when the head frame is around the low position.
The dial is preferably located closer to the head frame than a power switch mounted on front of the housing so that the dial can be easily accessed by a thumb of a user""s hand grasping the housing for control of the height of the head frame immediately after manipulating the power switch by the thumb. In this connection, the dial is located centrally of the housing with respect to a width dimension of the housing so that both of the left-handed and right-handed user can equally and easily manipulate the dial. The dial is preferred to include an indication for indicating the height of the head frame for easy confirmation by the user.
Further, the shaver may include a speed controller which varies a speed of the inner cutter in accordance with varying height of the head frame relative to the housing. More particularly, the speed controller is configured to increase the speed of the inner cutter as the head frame is lowered to the low position where the inner cutter is pressed against with increased contact pressure for shearing the hard hairs, thereby assuring successful shearing of the hard hairs with increased speed of the inner cutter.
The speed controller may comprise a position sensor for sensing the height of the head frame and a current-regulator which varies an electric current being supplied to the motor in accordance with an output of the position sensor.
When the inner cutter is driven to reciprocate relative to the outer cutter, the speed controller may be configured to vary a reciprocation amplitude of the inner cutter for varying the speed of the inner cutter. When the inner cutter is driven to rotate relative to the outer cutter, the speed controller is configured to vary a rotation speed of the inner cutter.
Alternatively, the shaver may include a controller which keeps the speed of the inner cutter constant irrespective of the varying height of the head frame.
In another preferred embodiment, the head frame is supported to a sleeve to be vertically movable relative to the sleeve. The sleeve is detachably mounted to an upper end of the housing and carries the height adjusting mechanism which varies the height of the head frame relative to the sleeve and includes a handle. Therefore, the height adjust mechanism can be assembled into a unit separate from the housing and can be therefore easily combined to the housing without causing any substantial interference with the structure of the housing, for example, the water-tight seal given to the housing for sealing the electric parts within the housing.
The head frame may be mounted to an additional support frame and is made vertically movable together therewith relative to the sleeve for height adjustment of the head frame. In this instance, the head frame surrounds the outer cutter to define itself the head cover which is movable together with the support frame.
The housing is closed at its upper end with a top member and is provided with the drive element projecting through the top member for driving connection with the inner cutter. The support frame is cooperative with the sleeve to form a barrier which surrounds the entire periphery of the top member irrespective of the position of the head frame relative to the housing. Thus formed barrier can well retain the sheared hairs on top of the housing and prevent undesired scattering of the hairs outwardly of the housing.
The handle mounted on the sleeve is configured to travel a path for adjusting the head frame between the high and low positions, which path is made longer than a vertical distance of the head frame between the high and low positions for enabling the height adjustment with a light operating force.
Associated with the handle is a click member which gives a click resistance to the handle movement. The click member is provided to develop the click resistance which is smaller when lowering the head frame from the high position to the low position than raising the head frame from the low position to the high position. Therefore, the small clicking resistance is added to the increasing downward spring force of the bias spring when the head frame is manipulated to move towards the low position, while the large clicking resistance is reduced by the upward spring force when the head frame is moving toward the high position. With this result, it is possible to manipulate the handle with a nearly equal operating force either when raising or lowering the head frame.
The support frame may have a stopper which engages with the sleeve so as to prevent an unintentional detachment of the support frame and the head frame from the sleeve.
These and still other advantageous features of the present invention will become more apparent from the following detailed description of the preferred embodiments when taken in conjunction with the attached drawings.